FI92001C - A method for inductively identifying a coin or similar material and an inductive sensor arrangement for carrying out the method - Google Patents

Description

92001

The present invention relates to a method for inductively identifying a coin or similar material based on the rotating currents generated by the inductive sensor magnetic circuit. a coin or the like bypassing the sensor's magnetic circuit at some distance. The invention also relates to an inductive sensor arrangement for carrying out this method, which sensor arrangement comprises a first inductive sensor and means for measuring a change in load generated by a coin or similar bypass to the first inductive sensor and storing the measurement data.

It is known to inductively determine the material of a coin or the like based on the change in load on the sensor caused by the coin or the like. However, significant sources of error in this case are, for example, the movement of the coin in the coin path of the coin counter, variations in the distance of the coin from the magnetic circuit of the inductive sensor and variations in the thickness of the coins or Senta-25 fry.

The object of the present invention is to provide a method and a sensor arrangement by means of which errors caused by distance and thickness variations can be eliminated from the measurement.

30 The above object can be achieved in connection with a method such as that described in the preamble, in which the method further comprises the steps of measuring the change in load caused by a coin or similar bypass at the same distance to a sensor 35 whose magnetic circuit is partially short-circuited. the rotational currents are also induced, and the ratio of said load changes is determined to obtain a coin or similar characteristic characteristic of the material.

The sensor arrangement according to the invention, in turn, is characterized in that it comprises, in addition to the parts mentioned in the preamble, a second inductive sensor whose magnetic circuit coin or the like is adapted to bypass substantially the same distance as the magnetic circuit of the first sensor. to which the circulating currents are also induced, means for measuring the change in load generated by the coin or similar bypass to the second inductive sensor and for storing the measurement data, and means for determining the ratio of said measurement data to obtain a coin or similar material characteristic.

20 A sensor arrangement very insensitive to coin or similar distance variations is obtained when the first and second inductive sensors each consist of two sensor circuits whose magnetic circuits are arranged opposite each other and between which the coin 25 or the like is adapted to pass and at the same distance from each other.

According to another embodiment of the invention, it is possible to proceed in such a way that the first and the second inductive sensor comprise a common sensor circuit, in the proximity of the magnetic circuit of which a partially magnetically short-circuiting material is arranged at the limits of this magnetic circuit.

A compact solution is also provided by the option in which the magnetic cores of the magnetic circuits of the first and second inductive sensors 35 are arranged crosswise on substantially the same axis.

In the following, the method according to the invention and the sensor arrangement suitable for carrying it out will be described in more detail with reference to the accompanying drawing, in which Fig. 1 Fig. 3 shows a schematic circuit diagram of one embodiment of a sensor arrangement according to the invention; -20 suitable for adapting magnetic circuits.

Figure 1 shows an exemplary circuit diagram for an inductive sensor suitable for use in the method and sensor arrangement of the invention. Such an inductive sensor first comprises an AC voltage source 25 which, through a resistor R, supplies the capacitor C and the coil L in parallel. Coil L is wound around the center pin of a pot-core type magnetic core. In this way, a magnetic circuit 1 is generated in the inductive sensor IA. When a metal coin or the like 4 is introduced in front of the magnetic circuit 1 at a distance d, the load on the oscillator changes. This change in load can be measured at the connection point O between the parallel connection of capacitor C and coil L and resistor R. Changes in oscillator load are based on the distance of the coin or the like 4 from the magnetic circuit 1 and the coin or centap. The magnetic circuit 1 causes circular currents in a coin or similar material, whereby these circular currents consume energy, which in turn is reflected in the load of the oscillator.

Fig. 2 shows, for example, the load R of the sensor IA reduced to resistance, which can be measured from the measuring point O of the oscillator of Fig. 1, in two different situations. When a piece of material such as a coin 4 is arranged in front of the magnetic circuit 1 of the sensor according to Fig. 1 at different distances, a curve RP is obtained, according to which the load R reduced to the sensor resistance increases as a function of the distance D up to the extreme value ROP 15, where the coin is at infinity. Then, when a piece of material, such as a thin copper foil, is dimensioned in front of the magnetic circuit 1, which is dimensioned so that at the frequency used, the magnetic flux almost passes through the copper foil in the curve RCu of Fig. 2. The thickness of the partially magnetically short-circuiting copper foil of the magnet-20 circuit 1 is then smaller than the penetration depth of the magnetic flux. For example, for copper, the penetration depth is 0.07 mm at a frequency of 1 MHz. The curve RCu in Figure 2 changes as a function of the distance D so that it approaches a load level lower than its initial value 25 when the coin is moved to an infinite distance from the magnetic circuit. In Figure 2, this value is denoted ROCu. When the values of the curves RP and RCu at the distance d are now determined according to Fig. 2, the values RP (d) and RCu (d) are obtained. According to the invention, it has been found that the quotient 30 (ROP-RP (d)) / (ROCu-RCu (d)) obtains a constant value typical of a coin or similar material, but independent of the distance d.

The method according to the invention is based on the observation just mentioned. In order to make use of this observation in practice, two measurements have to be made, in one of which the sensor magnetic circuit is open and thus closes mainly through air and in which the sensor magnetic circuit is partially "short-circuited" by the material in which the eddy currents are induced. Such a method 5 can be implemented with a wide variety of sensor arrangements. First, two separate sensors can be used, the magnetic circuits of which, such as a coin or the like, are arranged to be bypassed at the same distance and which are identical to each other except for a piece of material, such as a copper foil, fitted to the second magnetic circuit. According to the second alternative, only one inductive sensor can be used, the magnetic circuit of which, however, is sometimes partially "short-circuited" by a material in which the eddy currents can be induced. Thus, the two necessary measurements are performed successively in time at a sufficient frequency so that the position or distance of the coin or the like cannot change between measurements so that it has an effect on the measurement result.

Fig. 3 shows a sensor arrangement suitable for carrying out the method according to the invention, in which two inductive sensors IA1 and IA2 are used, in one of which the magnetic circuit is partially short-circuited by material 5. The arrangement of Fig. 3 thus has two inductive sensors IA1 and IA2, both consist of the sensor circuit API AP2, respectively, and the associated magnetic circuit 1, respectively 2. Of these, the latter, i.e. magnetic circuit 2, also contains its partially short-circuiting material piece 5. The mit-30 background data obtained from these inductive sensors, i.e. the may be, for example, circuits incorporated in a microprocessor. After measuring and storing these load changes, the ratio of these load changes in unit C, 35 can be determined, giving a characteristic figure typical of coin or the like 4 for the material 6 92001. This indicator can be displayed on the display 3 of the unit C, either as such or modified on the basis of the identification of the material performed by the comparison table stored in the unit C, into a characteristic character or word characteristic of the coin material. Unit C can in practice consist of a suitably programmed computer.

In connection with the sensor arrangement according to Fig. 3, it is essential that the magnetic circuits 1 and 2 are close enough to each other for the coin or the like 4 to pass them in use at substantially the same distance. However, the Antu riser is insensitive to coin jumping as well as being very tolerant of dirt and temperature fluctuations. However, Figure 4 shows the mutual arrangement of the magnetic circuits of the sensor arrangement according to the second embodiment of the invention, by means of which the sensor arrangement is made even more insensitive to variations in coin distance or possibly oblique direction of travel with respect to the magnetic circuits.

In the solution shown in Fig. 4, both the non-short-circuited and the partially short-circuited sensor in use consist of two inductive sensors, the magnetic circuits of which are arranged opposite each other, the coin 4 being arranged to pass between these magnetic circuits, and so that . Thus, the first sensor has two magnetic circuits 1A and IB and the second sensor has two magnetic circuits 2A and 2B, respectively. By now measuring the load changes in the oscillators in which the magnet-30 circuits 1A and IB are included and combining the measurement results thus obtained, for example by calculating their average, a measurement value is obtained which is completely independent of where the coin 4 is located in the magnetic circuit 1A and IB. That is, the distances d1 and d2 shown in Fig. 4 have no effect on this combined measurement result. Correspondingly, it is possible to proceed with the measurement results obtained from oscillators in which the magnetic circuits 2A and 2B are included. Thereafter, the procedure can be followed in the same way as shown in Fig. 3 with respect to the measured values stored in the sizes M1 and M2. As already mentioned above, the measurement results obtained in the arrangement according to Fig. 4 are independent of the point where the coin passes them between the magnetic circuits. Also, whether the coin 10 is located directly between the magnetic circuits is irrelevant to the reliability of the measurements.

Fig. 5 shows another embodiment of the sensor arrangement according to the invention, in which no pot-core type magnetic cores such as the sensors according to Figs. 1, 3 and 4 are used. Here, the sensor cores 14 and 24 are C-shaped and are arranged crosswise on substantially the same axis. Cores fitted to the cores are not shown in Figure 5 for clarity. In front of the core 24, a partially short-circuiting material piece 5 of its magnetic circuit 20 is arranged. . Since in this embodiment of Fig. 5 the center of the magnetic circuits is on the same axis, the measurement results obtained when using this embodiment are essentially independent of how skewed and at what distance the coin passes the magnetic circuits.

Instead of 30 C-shaped cores, other open heart shapes could naturally be used, such as open U or E-shaped cores, from which the central branch has been removed, without this affecting the measuring principle.

The method according to the invention and the sensor arrangement suitable for its implementation have been described above with the aid of only some exemplary embodiments, and it is to be understood that the structural solutions for the sensor arrangement in particular may vary without departing from the scope of the appended claims.

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Claims (6)

92001 A method for inductively identifying a coin or similar material based on changes in the load of an inductive sensor caused by a coin (4) of a magnetic circuit (1, 2) of a magnetic circuit (1, 2) of an inductive sensor (IA1, IA2) or a similar material, the method measuring said change or the like when passing a magnetic circuit (1) of a sensor (IA1) at some distance (d), characterized in that the method further comprises the steps of measuring the change in load on the sensor caused by the coin (4) or the like passing at the same distance (d) IA2), the magnetic circuit (2) of which is partially short-circuited by the material (5) to which the current flows are also induced, and the ratio of said load changes is determined in order to obtain a coin or similar characteristic characteristic of the material. 2. Inductive sensor arrangement for inductively identifying a coin or a centrifugal material based on changes in the inductive sensor load (s) of an inductive sensor (s) by an inductive sensor means (M1) for measuring the load change generated by the coin (4) or a similar bypass to the first inductive sensor (IA1) and storing the measurement data, characterized in that the arrangement further comprises a second inductive sensor (IA2) (2) having a magnetic circuit or the like is adapted to bypass at substantially the same distance (d) as the magnetic circuit (1) of the en-35 first sensor (IA1) and whose magnetic circuit (2) is partially magnetically short-circuited by the material (5) to which the current flows are also induced (M2). ) to another coin or similar bypass to measure the change in load-5 generated in the inductive sensor (IA2) and to store the measurement data, and means (C) for determining the ratio of said measurement data to obtain a coin or similar characteristic characteristic of the material. Sensor arrangement according to Claim 2, characterized in that the magnetic circuits (1, 2) of the first and second inductive sensors (IA1, IA2) are arranged successively in the direction of travel of the coin (4) or the like. Sensor arrangement according to Claim 2, characterized in that the first and the second inductive sensor each consist of two sensor circuits, the magnetic circuits (1A, IB, 2A, 2B) of which are arranged opposite one another and between which a coin or such that the magnetic circuits (ΙΑ, IB, 2A, 2B) of the first and second inductive sensors are substantially at the same distance from each other. A sensor arrangement according to claim 2, characterized in that the first and the second inductive sensor comprise a common sensor circuit, in the vicinity of the magnetic circuit of which a partially magnetically short-circuiting material body is arranged at intervals of this magnetic circuit. Sensor arrangement according to Claim 2, characterized in that the magnetic cores (14, 24) of the magnetic circuit of the first and second inductive sensors are arranged crosswise on substantially the same axis. I I 92001